Caption: This composite image shows the galaxy cluster 1E 0657-56, also known as the
"bullet cluster", formed after the collision of two large clusters of
galaxies. Hot gas detected by Chandra is seen as two pink clumps in the
image and contains most of the "normal" matter in the two clusters. An
optical image from Magellan and the Hubble Space Telescope shows galaxies
in orange and white. The blue clumps show where most of the mass in the
clusters is found, using a technique known as gravitational lensing. Most
of the matter in the clusters (blue) is clearly separate from the normal
matter (pink), giving direct evidence that nearly all of the matter in the
clusters is dark. This result cannot be explained by modifying the laws of
gravity.